This invention relates to an improved construction and relationship of parts to support and impart rotary motion to a renewable air filter cartridge located within a filter housing for supplying filtered air to the carburetor of an internal combustion engine. More particularly, the present invention relates to support apparatus incorporating impeller means contacted by filtered air for rotating the renewable filter cartridge and at the same time an arrangement of parts to bring about a periodic interruption of the flow of air through a small segment of the filter cartridge for releasing adhered particulate matter under the influence of a centrifugal force to thereby clean the renewable filter cartridge during the filtering operation.
As is well known in the art, the carburetor of an internal combustion engine is provided with an air filter assembly to deliver filtered air through an opening in the bottom of a housing which has an annular shape and includes a removable cover to permit replacement of the renewable filter cartridge. The housing of the air filter assembly has a hollowed-out shape and provided with an annular gasket on its floor surface in a surrounding relation with the air discharge port communicating with the carburetor. The gasket is used to form an airtight seal with the bottom surface of the filter which is also sealed in an airtight manner by a gasket provided on the cover for the housing. The incoming air delivered through an opening in the side wall of the housing is drawn through the filter cartridge by negative air pressure in the carburetor.
I have discovered that this construction of an air filter assembly has brought about an inefficient filtering system for air because the incoming air passing into the filter housing is drawn preferentially through the immediate peripheral surface which is most adjacent to the air inlet pipe with respect to the filter cartridge. As s result, a very small segment of the air filter cartridge filters a significantly greater volume of air while the remaining segmental portion of the filter cartridge contributes far less to the filtering of air. As the portion of the air filter cartridge most adjacent the air inlet pipe becomes clogged, passage of air through the filter is lessened because there is an increasingly larger portion of air that must travel a longer distance around the filter cartridge before passing through it, thus further increasing the air friction within the filter housing and reducing the amount of air supplied to the internal combustion engine. This, of course, deprives the internal combustion engine of the proper volume of air to effect an efficient and complete combustion of the air-gas mixture. This condition, of course, is ever changing in time because the filter cartridge, over a period of time, becomes clogged to a greater and greater extent.
In my prior U.S. Pat. No. 3,898,066, there is disclosed an air filter assembly wherein an annular filter element is supported for rotation within a housing. Turbine blades extend from cover plates at the top and bottom surfaces of the filter element. An air feed pipe opens out of the side wall of the housing for directing the incoming air in a direction tangentially toward the annular filter element for contact with the turbine blades to produce the desired rotation of the filter element. The filter element is rotatably supported by bearing surfaces carried either by the bottom wall of the housing or by interfitting annular flanges projecting from the top surface of the cover plate for the filter and the cover plate for the filter housing. While this prior form of an air filter assembly provides the desired feature of rotating the air filter and thereby overcome the aforementioned disadvantage in regard to a stationary filter element within a filter housing, it nevertheless suffers from the disadvantage that the arrangement and construction of parts employed to support the filter element for rotation are costly and cumbersome to disassemble for replacing the renewable filter element.